Base station transceiver sub-system and frame offset allocation method thereof

ABSTRACT

The invention disclosed herein relates to a base station transceiver sub-system, where when data is transmitted/received via radio in predetermined time long frame units, one frame offset of a plurality of frame offsets after dividing the time length is allocated to each traffic channel, and the radio interface  50  and the ATM interface are synchronized using this frame offset. In this base station transceiver sub-system, the fluctuation of cells on an ATM line is tolerated for a predetermined frame offset width, and considering the cell transmission enabled band according to said tolerated fluctuation width, a same frame offset is allocated to a plurality of traffic channels so as to control the generation of fragmentation.

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a base station transceiversub-system and a frame offset allocation method thereof, and moreparticularly to a base station transceiver sub-system and a frame offsetallocation method thereof which tolerates a predetermined frame offsetwidth of fluctuation of cells in an ATM line, and allocates a same frameoffset to a plurality of traffic channels so as to control thegeneration of fragments.

[0002] When the base station transceiver sub-system 1 (FIG. 17) in amobile radio communication system transmits frames to radio terminals#A2 a-#C2 c with a 20 ms frame as the transmission unit, one of the 16levels of offsets with a 1.25 ms interval (hereafter frame offset) isattached to a frame for transmission. FIG. 18 is a diagram depictingtransmission timing in a radio interface, where the offset of the frameFA to be transmitted to the radio terminal #A is 0 ms, the offset of theframe FB to be transmitted to the radio terminal #B is 1.25 ms, and theoffset of the frame FC to be transmitted to the radio terminal #C is2.50 ms.

[0003] When a base station controller 3, on the other hand, generates 20ms frames and transmits them to the base station transceiver sub-system1, the frames must be transmitted to the radio terminal with apredetermined frame offset without a delay. For this, the radio stationtransceiver sub-system 1 and the base station controller 3 synchronizein 20 ms units, and both know the head position of the frame (positionat frame offset=0). In order to synchronize the ATM interface and theradio interface, the base station controller 3 transmits 20 ms frames onan ATM line with a delay of 1.25 ms offset. In other words, on the ATMline as well, a 1.25 ms unit offset is attached to a frame, just likethe radio interface, so as to synchronize with the radio interface. Forexample, if offsets 0, 1 and 2 (in terms of time 0, 1.25, 2.50 ms),shown in FIG. 18, are added to the frames FA, FB and FC on the radiointerface, frames (actually cells) are transmitted at the transmissiontiming at the same offsets 0, 1 and 2 (in terms of time 0, 1.25, 2.50ms) even on the ATM line. FIG. 19 is a diagram depicting transmissiontiming on the ATM line, where frames are divided into cells and cellsCL_(FA), CL_(FB) and CL_(FC) corresponding to frames FA, FB and FC aretransmitted at the transmission timing of the offsets 0, 1 and 2.

[0004] On the ATM line, the maximum number of bits that can betransmitted during one offset period is limited, but within this rangeof the maximum value, one frame offset can be allocated to a pluralityof traffic channels. FIG. 20 is a diagram depicting transmission timingwhen one frame offset is allocated to a plurality of traffic channels,and shows the case when two traffic channels are allocated to offsets 0and 2 respectively.

[0005] If cells can be transmitted with a smaller gap (unused band) ineach offset, transmission efficiency can be increased and the number ofusers to accommodate can be increased. Therefore band management isnecessary to determine how much traffic (traffic channels) is allocatedto one offset.

[0006] The mobile radio system comprised of the base station transceiversub-system 1 and the base station controller 3 shown in FIG. 17conventionally handle voice data and low speed fixed-length data.Therefore traffic data of a predetermined traffic channel is merelytransmitted mechanically in a predetermined frame offset on an ATM linewhere no problems occur. In other words, such problems as fluctuationand fragmentation due to the coexistence of such fixed-length data asvoice data and variable length data where the data length is different,do not occur.

[0007] Generation of Fluctuation

[0008] Recently, however, users began handling such fixed-length data asvoice and such variable length data as packets. In a mobilecommunication system using portable phones as well, the demand for suchwide band data communication as packet communication is increasing. Witha radio interface, high-speed communication has become possible, wherethe number of bits that can be transmitted in a 20 ms frame is doubleor, sometimes, more than ten times, compared with voice and conventionallow speed data communication. In such a high-speed communication, thenumber of bits in a 20 ms frame which can be transmitted on an ATM lineincreases, and in some cases, a full 20 ms frame (transmission data of 1traffic channel) cannot be transmitted by a 1 frame offset on an ATMline, which causes fluctuation. For example, as FIG. 21 shows, when wideband communication data D_(A), which exceeds the 1 frame offset on theATM line, and narrow band communication data D_(B), such as voice, areallocated to the frame offset=0, voice delays and fluctuation occurs tovoice traffic. Once fluctuation is generated, the radio interface andthe ATM interface cannot be synchronized, and frames cannot betransmitted/received correctly. In the above example, if the voice istransmitted at the position of frame offset=0, the wide band datadelays.

[0009] Fragmentation

[0010] Data communication involves various bit rates, from a low rate toa high rate. When data communication and low speed voice communicationcoexist, communication in the narrow band, such as voice and low speeddata, may be distributed to each offset, as shown in FIG. 22. If suchdistribution is generated, fragmentation of bands increases, and a frameoffset to allocate may not exist in wide band (high-speed)communication. FIG. 22 is the case when a frame offset cannot beallocated to traffic channel having a 1.5 frame band because there is nocontinuous empty band having a 1.5 frame band. However, as shown in FIG.23, if the traffic channels in the narrow band concentrate to the frameoffset=0, and fragmentation decreases, then frame offset=1 and 2 haveempties, and a traffic channel in the wide band can be allocated to theframe offset=1 for transmission.

SUMMARY OF THE INVENTION

[0011] With the foregoing in view, it is an object of the presentinvention to absorb fluctuation so as to transmit/receive datacorrectly.

[0012] It is another object of the present invention to control thegeneration of fragments of bands while absorbing fluctuation.

[0013] It is still another object of the present invention to allocate atraffic channel, which is allocated to each frame offset, while managingbands.

[0014] A first aspect of the present invention is a base stationtransceiver sub-system which transmits/receives data to/from a mobilestation via radio, and transmits/receives data in cells to/from a basestation controller via a transmission line, comprising: (1) an offsetallocation block which allocates one frame offset of a plurality offrame offsets after dividing a predetermined time length to each trafficchannel when data is transmitted/received via radio in the predeterminedtime long frame units; (2) a radio interface which transmits frames of apredetermined traffic channel at timing according to the frame offsetallocated to the traffic channel; (3) a transmission line interfaceblock which divides the frame of each traffic channel into cells andtransmits/receives the cells to/from the base station controller via thetransmission line at timing according to the frame offset allocated tothe traffic channel; and (4) a fluctuation tolerance block whichtolerates the fluctuation of the cells on the transmission line for apredetermined frame offset width, wherein the offset allocation blockallocates a same frame offset to a plurality of traffic channelsconsidering a data transmission enabled band according to the toleratedfluctuation width.

[0015] The fluctuation tolerance block further comprises: a memory forstoring frames for a period according to the fluctuation width, and afluctuation control block which reads frames from the memory and inputsthe frames into a modulation block at a predetermined timing. The offsetallocation block sets the band management range considering thetolerated fluctuation width as the data transmission enabled bandcorresponding to each one of the plurality of frame offsets, andallocates each frame offset to a plurality of traffic channels so as notto exceed the band management range.

[0016] A second aspect of the present invention is a frame offsetallocation method for a base station transceiver sub-system, comprisingan offset allocation block, a radio interface, and a transmission lineinterface, comprising steps of: (1) tolerating the fluctuation of frameson the transmission line for a predetermined frame offset width; and (2)allocating a same frame offset to a plurality of traffic channelsconsidering the data transmission enabled band according to thetolerated fluctuation width. When a traffic channel is allocated, a bandmanagement range is set according to the tolerated fluctuation widthcorresponding to each one of the plurality of frame offsets, and eachframe offset is allocated to a plurality of traffic channels so as notto exceed the band management range.

[0017] According to the present invention, frame synchronization betweenthe radio interface and the ATM interface can be guaranteed by absorbingfluctuation and the frames can be transmitted/received correctly. Alsothe fragmentation of a band can be controlled while absorbingfluctuation, traffic channels can be allocated in a wide band, and theband can be used effectively. Also 1 frame offset can be allocated to aplurality of traffic channels while managing the band of a trafficchannel to be allocated to each frame offset, and the band can be usedeffectively.

[0018] Other features and advantages of the present invention will beapparent from the following descriptions with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1A, FIG. 1B and FIG. 1C are diagrams depicting frame offsets;

[0020]FIG. 2 is a diagram depicting the decision of an offsetconsidering fluctuation;

[0021]FIG. 3 is a diagram depicting frame offset allocation whenfluctuation is tolerated on an ATM line;

[0022]FIG. 4A, FIG. 4B, FIG. 4C and FIG. 4D are diagrams depicting frameoffset allocation considering the tolerated fluctuation range;

[0023]FIG. 5 is a diagram depicting traffic channel allocation whenavailable bands in the band management range have decreased;

[0024]FIG. 6 is a diagram depicting the state after traffic channelallocation when available bands in the band management range havedecreased;

[0025]FIG. 7 is a block diagram depicting a base station transceiversub-system and a base station controller;

[0026]FIG. 8 is a diagram depicting the protocol structure between BSCand BTC;

[0027]FIG. 9 is a diagram depicting the format of an AAL-type 2 cell;

[0028]FIG. 10 is a diagram depicting the format of an AAL-type 2 celland a short cell;

[0029]FIG. 11 is a diagram depicting the concept of the transfer systemby AAL-type 2;

[0030]FIG. 12 is a block diagram depicting a base band processing block;

[0031]FIG. 13 is a diagram depicting a resource management table;

[0032]FIG. 14 shows an allocation processing flow of a traffic channel;

[0033]FIG. 15 shows a processing flow when a channel is disconnected;

[0034]FIG. 16 shows a fluctuation absorption processing flow;

[0035]FIG. 17 is a diagram depicting a mobile communication system;

[0036]FIG. 18 is a diagram depicting transmission timing in a radiointerface;

[0037]FIG. 19 is a diagram depicting transmission timing on an ATM line;

[0038]FIG. 20 is a diagram depicting transmission timing when 1 frameoffset is allocated to a plurality of channels;

[0039]FIG. 21 is a diagram depicting fluctuation which is generated onan ATM line;

[0040]FIG. 22 is a diagram depicting the fragmentation of a band on anATM line; and

[0041]FIG. 23 is a diagram depicting the case when the fragmentation ofa band is minor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] (A) Overview of the Present Invention

[0043] (a) Frame Offset

[0044] A mobile radio communication system comprises a base stationtransceiver sub-system (BTS) 10 and a base station controller (BSC) 20which are inter-connected via an ATM line, as shown in FIG. 1A. The basestation transceiver sub-system 10 receives 20 ms frames (actually cells)per channel from the base station controller 20 via the ATM line 40, andtransmits the 20 ms frames to a mobile station 30 via a radio interface50. Both the base station transceiver sub-system 10 and the base stationcontroller 20 use a 20 ms frame as the transmission unit, adds one ofthe 16 levels of offset with a 1.25 ms interval to a frame, andtransmits the frame, as shown in FIG. 1B.

[0045] The base station transceiver sub-system 10 and the base stationcontroller 20 synchronize in 20 ms units, and both know the headposition of the frame (position of frame offset=0). To transmit 20 msframes (cells) of a predetermined traffic channel, the base stationcontroller 20 transmits the frames (cells) at transmission timingaccording to the frame offset allocated to the traffic channel (frameoffset=2 in the case of FIG. 1B), and the base station transceiversub-system 10 adds as the frame offset according to the traffic channel(frame offset=2 in this case) to the frames, and transmits it to themobile terminal 30 via the radio interface 50, as shown in FIG. 1C.Actually, the base station transceiver sub-system 10 employs a means(mentioned later) of tolerating delay for the total M frame offset widthconsidering transmission delay on the transmission line, processingdelay and fluctuation of phases of cells. Therefore a time delaycorresponding to the M frame offset is tolerated between the frameoffset n on the ATM line and the frame offset n on the radio interface.

[0046] When frames of a predetermined traffic channel are received fromthe mobile station 30, the base station transceiver sub-system 10packetizes the frames into cells, and transmits the cells to the basestation controller 20 via the ATM line 40 according to the trafficchannel.

[0047] (b) Absorption of Fluctuation

[0048]FIG. 2 is a diagram depicting how to decide the offset consideringdelay (fluctuation).

[0049] To determine a frame offset position on an ATM line, thetransmission delay D_(TA) (=Ta−Tb) on an ATM line and the internalprocessing delay D_(TB) (=Tb′−Tc) of the base station transceiversub-system 10 from receiving 20 ms frames from the base stationcontroller 20 to transmitting the 20 ms frames to the radio interface50, must be considered. In addition to these delays, the presentinvention decides the frame offset considering fluctuation. In theexample in FIG. 2, the fluctuation tolerance range for the total M (=5)frame offset width is set considering 1 frame offset as the transmissiondelay D_(TA) of the ATM line, 1 frame offset as the base stationinternal processing delay D_(TB), and 3 frame offsets as the fluctuationabsorption range D_(J). This tolerated fluctuation range can be set bystoring frames (traffic data) in a memory for the period according tothis range, and reading the frames from this memory at a predeterminedtiming. By setting the tolerated fluctuation range, a margin for thetime delay corresponding to the M frame offset is generated between theframe offset n on the ATM line and the frame offset n on the radiointerface.

[0050] The effect of the tolerated fluctuation range will now bedescribed with reference to FIG. 3. It is assumed that a traffic channelof wide band data (for a 1.5 frame offset) is allocated to the frameoffset=0. By this, fluctuation is generated at the narrow band frame F0which exists at the frame offset=0, and frame F0 fluctuates to the frameoffset=1. However, the tolerated fluctuation range is up to a 5 frameoffset, so the base station transceiver sub-system 10 can transmit thisframe F0 at the radio frame offset=0 without delay.

[0051] (c) Controlling Fragmentation

[0052] In the present invention, band management to control thegeneration of fragmentation is performed based on the fact thatfluctuation for up to M frame offsets is tolerated by setting thetolerated fluctuation range. FIG. 4(A) is a state where the trafficchannel T0 is allocated to the frame offset=n, and FIG. 4(B) is a statewhere the traffic channel T1 is also allocated to the frame offset=n.This is because there is sufficient remaining available band at theframe offset=n with respect to the band of the traffic channel T1. Thenthe band for the traffic channel T2 is secured.

[0053]FIG. 4(C) is an example of conventional offset allocation wherethe generation of fluctuation is not tolerated. In the frame offset=n,there is no empty to secure a band required for the traffic channel T2.Therefore the traffic channel T2 is allocated to the frame offset n+1.With such an allocation, however, some band Bn′ of the frame offset=nwhich is not used remains as a fragment. This fragment is used if atraffic channel whose band is smaller than the band Bm′ is generated inthe feature, but remains otherwise. If such a status is generated ateach frame offset position and many fragments are generated, acontinuous empty band required for securing the band of the trafficchannel for which connection is requested does not exist, even though asufficient empty band exists on the total ATM line, and the connectionof this traffic channel is impossible.

[0054] So in the present invention, the traffic channel is allocated toa frame offset considering the tolerated fluctuation range. In theexample in FIG. 4(D), the tolerated fluctuation range is the length ofthe M (=3) offset. By setting the tolerated fluctuation range, the bandwidth of the frame offset n is regarded as 4 offsets, including thetolerated fluctuation. In other words, the band management range of theoffset n is 4 offsets, from n to n+3, where a plurality of trafficchannels can be allocated to the frame offset n within a range whichdoes not exceed the band width of this band management range. This isbecause fluctuation is controlled within the tolerated fluctuationrange, even if the traffic of a predetermined traffic channel fluctuatesup to the n+3 offset by allocating a plurality of traffic channels tothe frame offset n, and the frame is delivered by allocating a pluralityof traffic channels to the frame offset n, before the frame offset n onthe radio interface. The frame offset n on the radio interface isactually delayed 3 offsets from the frame offset n on the ATM interface.

[0055] Therefore the traffic channel T2 can be allocated to the offsetn, as shown in FIG. 4(D). In this case, the traffic channel T2 uses aband up to n+1, exceeding the offset position n, but is still within thetolerated fluctuation range. So the base station transceiver sub-system10 can receive the traffic data of the traffic channel T2 before theradio frame offset n, performs spread modulation on the traffic data,and transmits the spread data. The emptyband in the offset n does notfragment and remains, and the band can be used efficiently.

[0056]FIG. 5 is a traffic channel allocation example when the remainingavailable band Bn′, which can be used within the band management rangeBn of the offset n, is decreased. Although the traffic channel T5attempts allocation to the offset n, the empty band Bn′ at the n+3position in the band management range Bn of the offset n is insufficientfor allocating the traffic T5. In this case, the offset is shifted ton+1, and it is checked whether the band management range Bn+1 of theoffset (n+1) has sufficient empty. Considering the tolerated fluctuationrange (3 offsets in this example), the band Bn+1′, which is the total ofwhat remains of n+3 and n+4, is empty. Therefore the traffic channel T5can be allocated to the offset n+1. FIG. 6 shows this state. Since thetraffic T0-T4 allocated to the offset n substantially uses the band ofthe offset n+3, the transmission of T5 ends at the position n+4, but isstill within the tolerated fluctuation range Bn+1 of the frame offset(n+1). Therefore the base station transceiver sub-system 10 can receivethe frames of the traffic channel T5 from the ATM line before the radioframe offset n+1, and modulates and transmits the frames.

[0057] (B) Configuration of Base Station Transceiver Sub-system and BaseStation Controller

[0058]FIG. 7 is a block diagram of a base station transceiver sub-systemand a base station controller, where 10 a-10 b are the base stationtransceiver sub-systems (BTS), 20 is a base station controller (BSC)which controls a plurality of base stations (BTS), and 30 a-30 c aremobile stations which exist in radio zones corresponding to the basestations 10 a and 10 b, and communicate with the corresponding basestations via radio. The base station transceiver sub-systems (BTS) 10a-10 b and the base station controller (BSC) 20 are connected by the ATMline 40, and the base station transceiver sub-system 10 a-10 b receive20 ms frames (actually cells) from the base station controller 20 viathe ATM line, and transmits the 20 ms frames to the mobile station viathe radio interface.

[0059] The base station transceiver sub-systems 10 a and 10 b have thesame configuration, comprising: an AMP block 11, a radio block 12, abase band signal processing block 13 which performs base band signalprocessing, a controller 14 in the base station transceiver sub-systemwhich controls channel allocation and power management, and thetransmission line interface block 15. The amplifier block 11 amplifiesthe transmission/reception signal, and the radio block 12 converts thefrequencies of high frequency signals, which are input from the antennavia the amplifier block, to a base band signal, and converts base bandsignals to high frequency signals and inputs the high frequency signalsto the antenna via the amplifier block. The base band signal processingblock 13 performs such processing as spread and orthogonal modulation ona plurality of channels of communication signals (various controlsignals, voice signals, data signals, etc.), inputs the modulatedsignals to the radio block 12, and performs such processing asorthogonal detection, inverse spread and data demodulation on aplurality of channels of communication signals, which are input from theradio block 12, and inputs the demodulated data to the transmission lineinterface block 15 and the control block 14. The transmission lineinterface block 15 performs N channels of signal multiplex and signaldemultiplex processing, and performs signal conversion processingbetween the base station transceiver sub-system (BTS)/base stationcontroller (BSC). The controller 14 in the station performs call controland transmission power management control, and performs traffic channelsetup control related to the present invention.

[0060] The base station controller 20 comprises base station interfaceblocks 21 a and 21 b, a clock generation block 22, a control block 23,an ATM switch/processing block 24, a hand off processing block 25, atraffic supervisory control block 26, voice signal processing blocks 27a and 27 b, switch interface blocks 28 a and 28 b, a packet signalprocessing block 29 a, and a PDSN interface block 29 b. The base stationinterface blocks 21 a and 21 b perform signal format conversion andlevel conversion between the base station transceiver sub-systems 10 aand 10 b and the switches, and the clock generation block 22 generatesreference clocks and various timing signals. The control block 23controls the base station controller in general, and the ATMswitch/processing block 24 transmits signals from each base stationtransceiver sub-system 10 a and 10 b to a predetermined port at theswitch station side, and transmits signals from the switch station sideto a predetermined base station transceiver sub-system. The hand offprocessing block 25 performs hand off control, the traffic supervisorycontrol block 26 supervises the traffic channel (traffic) for each basestation transceiver sub-system, the voice signal processing blocks 27 aand 27 b performs conversion between the voice encoding system of radiozones (between a terminal and base station controller) and the voiceencoding system (PCM) of a public network, and the switch interfaceblocks 28 a and 28 b performs signal conversion processing between thebase station controller and the switch station. The packet signalprocessing block 29 a performs packet signal processing.

[0061] (C) Frame Format

[0062] (a) Protocol Structure

[0063]FIG. 8 is a diagram depicting a protocol structure between BSC andBTS where E1 is used for the physical layer, the ATM layer is on thephysical layer, the AAL layer is thereon, and the application layer ison top. The AAL layer uses AAL-type 2 for transferring trafficinformation, and uses AAL-type 5 for transferring control information,as shown in (1) and (2).

[0064] In the field of mobile communication, data is converted to a lowbit rate data format by compression in order to use the communicationband effectively. When such low speed bit rate information is embeddedinto a payload of a standard ATM cell, it takes time for the payload ofone ATM cell to be filled with data. This delays data and tends to dropthe quality of communication. So, as a method to transmit low bit rateinformation with less delay, a multiple transfer system called AAL-type2 is recommended in ITU-T I.363.2. This transfer method, AAL-type 2, issuitable for transferring low bit rate information used for mobilecommunication networks, and can use a band effectively with few delays.

[0065] (b) AAL-type 2 Format

[0066]FIG. 9 and FIG. 10 are diagrams depicting the format of AAL-type2. FIG. 11 is a diagram depicting the concept of a transfer system basedon AAL-type 2. As FIG. 9 shows, an ATM cell in AAL-type 2 format iscomprised of a standard cell header and a standard cell payload, where a1 byte start field STF and 1 or more short cells are mapped in thestandard cell payload.

[0067] The start field STF is comprised of (1) an offset field OFS wherethe pointer to indicate the first position of the first short cell(offset value) is stored, (2) a field SN where a 1 bit sequence numberis stored, and (3) a parity field P.

[0068] A short cell is created for each traffic channel, and iscomprised of (1) a fixed-length short cell header and (2) a variablelength short cell payload. The short cell header includes {circle over(1)} a short cell connection identifier (channel identifier) CID foridentifying the short cell connection (traffic channel), {circle over(2)} a length indicator (LI) for indicating the payload length of theshort cell, and {circle over (3)} a user user identifier (UUI), and theshort cell payload includes low bit rate traffic information.

[0069] In the AAL-type 2 cell, a plurality of short cells are stored ina multiplexed state. If a part of the short cells exceed the payload ofone AAL-type 2 cell, the remaining part of the short cells are mapped tothe next AAL-type 2 cell, as shown in FIG. 11 (overlap). And theAAL-type 2 cell is transmitted on a predetermined ATM connectionaccording to the VPI/VCI stored in the header.

[0070] (D) Configuration of Base Station Transceiver Sub-system

[0071]FIG. 12 is a block diagram depicting a part of the base stationtransceiver sub-system.

[0072] In the transmission line interface block 15, the line terminatingblock 15 a perform E1 interface termination processing, and thepreprocessing block 15 b extracts cells from the received frame atreception, and performs synchronization processing using HEC. Thedemultiplexing block (DMUX) 15 c demultiplexes the traffic informationTDT of AAL-type 2, and control information CDT of AAL-type 5 and outputsthis information.

[0073] The control block 14 performs a predetermined control processingbased on the control information. For example, the resource managementblock 14 a performs allocation processing to allocate traffic channelsto frame offsets when a traffic channel setup request is received fromthe base station controller 20, and also performs allocation releaseprocessing when a traffic channel release request is received. Theallocation result is stored in the resource management table 14 b, sothat the later mentioned processor 13 c can use it. FIG. 13 is a blockdiagram of the resource management table, where {circle over (1)} theremaining available band B_(Rn) in the band management range and {circleover (2)} the identifier of the allocated traffic channel and the bandthereof are stored corresponding to the frame offset n=0-15.

[0074] The ATM cell demultiplexing block 15 d demultiplexes the ATM cellinto AAL-type 2 cells (short cells) and the short cell demultiplexingblock 15 e demultiplexes short packets (traffic information) from theshort cells, and inputs the packets to the packet reception processing &S/P conversion block 13 a. The packet reception processing & S/Pconversion block 13 a performs a CRC check and an HEC check, performsserial/parallel conversion, and stores parallel data in the memory 13 b.The processor 13 c reads the frames (traffic data) of one or moretraffic channels allocated to the target frame offset n from the memory13 b at a predetermined timing, considering the tolerated fluctuationrange for each frame offset n (n=0-15), inputs the traffic data of eachchannel which was read to the spread modulation block according to thetraffic channel of the digital modulation/demodulation block 13 d, andtransmits the spread modulated data via the radio block.

[0075] The processor 13 c stores data which was demodulated by theinverse spread demodulation block of each channel in the digitalmodulation/demodulation block 13 d in the memory 13 e. The packettransmission processing block & P/S conversion block 13 f reads the datafrom the memory 13 e, performs HEC insertion and CRC insertionprocessing and parallel/serial conversion, and inputs the serial data tothe short cell assembly block 15 f. The short cell assembly block 15 fassembles AAL-type 2 cells (short cells), and the ATM cell assemblyblock 15 g assembles ATM cells from the short cells, and inputs the ATMcells to the multiplexing block 15 h. The multiplexing block 15 hmultiplexes the traffic information of AAL-type 2 and the controlinformation of AAL-type 5, and inputs the multiplexed information to thepreprocessing block 15 b, and the preprocessing block 15 b calculatesand inserts HEC into multiplexed information at transmission, and inputsthe information to the line terminating block 15 a. The line terminatingblock 15 a directly maps the multiplexed ATM cells to the E1 frame.

[0076] (E) Allocation Processing

[0077] (a) Traffic Channel Allocation Processing

[0078]FIG. 14 depicts a traffic channel allocation processing flow bythe resource management block 14 a.

[0079] When a traffic channel connection request is detected (Step 101),the resource management block 14 a sets n=0 (Step 102), and acquires theremaining available band B_(Rn) in the band management range of offset nfrom the resource management table 14 b (Step 103).

[0080] Then the resource management block 14 a checks whether theremaining available band B_(Rn) is greater than the traffic transmissionband B_(T) of the traffic channel for which connection is requested(Step 104), and if smaller, n is changed (n+1→n, Step 105), n>16 ischecked (Step 106), and if n is smaller than 16, processing after Step103 is repeated. However, if n>16 in Step 106, the resource managementblock 14 a regards this as allocation disabled, and returns a resourcesecuring disabled response (channel connection disabled) to the channelconnection request source (Step 107).

[0081] If B_(Rn)≧B_(T) in Step 104, the requested traffic channel isallocated to the frame offset n (Step 108). Then the remaining availableband B_(Rn) in the frame offset n is updated by the following formula.

B_(Rn)−B_(T)→B_(R) (Step 109)

[0082] Then the resource management block 14 a checks which frame offsetand how many bands will be allocated for the band B_(T) of the trafficchannel (Step 110). Here the bands B_(na)˜B_(nb) of the frame offsetsna˜nb are allocated to the traffic channel respectively.

[0083] Then a plurality of frame offsets where at least one of the frameoffsets na˜nb is included in the band management range are determined,and the remaining available bands of each frame offset is updated basedon the allocated band Bna˜Bnb (Step 111).

[0084] Then the resource management block 14 a updates the content ofthe resource management table 14 b (Step 112), and notifies the channelconnection request source that the channel connection is possible andinformation on the allocated frame offsets (Step 113).

[0085] By this, the base station controller 20 packs the frames (shortcells) of each traffic channel into ATM cells, and transmits the ATMcells at the notified timing of the frame offset. Referring to theresource management table 14 b, the processor 13 c identifies one ormore traffic channels allocated to the target frame offset n, and readsthe traffic data of this traffic channel from the memory 13 b at apredetermined timing considering the tolerated fluctuation range, andinputs the traffic data to the digital modulation/demodulation block 13d.

[0086] (b) Allocation Processing when Traffic Channel is Disconnected

[0087]FIG. 15 depicts the allocation processing flow by the resourcemanagement block 14 a when a traffic channel is disconnected. When atraffic channel disconnection request is detected (Step 201), theresource management block 14 a determines a frame offset m where thetraffic channel Ti, for which disconnection is requested, is allocated,referring to the resource management table 14 b (Step 202). Then theresource management block 14 a acquires the remaining available bandB_(Rm) of the frame offset m and the band B_(Ti) of the traffic channelTi from the resource management table 14 b (Step 203), and updates theremaining available band B_(Rm) of the frame offset m by the followingformula.

B_(Rm)−B_(Ti)→B_(Rm) (Step 204)

[0088] Then the resource management block 14 a checks which frame offsetand how many bands will be released (Step 205). Here the bands Bra˜Brbof the frame offsets ra˜rb are released respectively.

[0089] Then a plurality of frame offsets where at least one of the frameoffsets ra˜rb is included in the band management range are determined,and the remaining available bands of each frame offset are updated basedon the bands Bra˜Brb which are released (Step 206).

[0090] (F) Fluctuation Absorption Processing

[0091]FIG. 16 shows a flow of fluctuation absorption processing.

[0092] If the tolerated fluctuation range is the M frame offset, thenthe traffic data (short cell data) for at least the M frame offset issequentially stored in the memory 13 b (FIG. 12) (Step 301), and it ismonitored whether the transmission timing at the target offset frame nhas been reached. When the transmission timing at the target offsetframe n has been reached, the traffic channel allocated to this targetoffset frame is identified referring to the resource management table 14b (Step 303), the traffic data of this identified traffic channel isread from the memory 13 b, and is input to the corresponding CDMA spreadmodulation block (Step 304). By this, each spread modulation blockperforms spread modulation, and transmits the transmission data via theradio interface (Step 305).

[0093] Then the target frame offset n is changed, and the processingafter Step 301 is repeated.

[0094] In the above description, a case when allocation processing isperformed by the control block 14 was described, but the allocationprocessing can also be performed by the processor 13 c.

[0095] According to the present invention, frame synchronization betweenthe radio interface and the ATM interface can be secured by absorbingfluctuation, so frames can be correctly transmitted/received.

[0096] Also according to the present invention, the generation offragmentation of bands can be controlled while absorbing fluctuation, sothat traffic channel allocation in a wide band is possible, and bandscan be used effectively.

[0097] Also according to the present invention, a plurality of trafficchannels can be allocated to one frame offset while managing the band oftraffic channels to be allocated to each frame offset, which allowseffective use of a band.

[0098] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. A base station transceiver sub-system whichtransmits/receives data to/from a mobile station via radio, andtransmits/receives data in cells to/from a base station controller via atransmission line, comprising: an offset allocation block whichallocates to each traffic channel one of a plurality of frame offsetsgenerated by dividing a predetermined time length when data istransmitted via radio in said predetermined time length frame units; aradio interface which transmits frames of a predetermined trafficchannel at timing according to the frame offset allocated to saidtraffic channel; a transmission line interface which assembles cellsusing frame of each traffic channel and transmits/receives the cellsto/from the base station controller via the transmission line at timingaccording to the frame offset allocated to said traffic channel; and afluctuation tolerance block which tolerates the fluctuation of a cell onthe transmission line for a predetermined frame offset width, whereinsaid offset allocation block allocates a same frame offset to aplurality of traffic channels considering the data transmission banddetermined by said tolerated fluctuation width.
 2. The base stationtransceiver sub-system according to claim 1, wherein said fluctuationtolerance block further comprises: a memory for storing frames for aperiod according to said fluctuation width; and a fluctuation controlblock which reads frames from said memory and inputs the frames into amodulation block at a predetermined timing.
 3. The base stationtransceiver sub-system according to claim 1, wherein said offsetallocation block sets a band management range, considering saidtolerated fluctuation width, as said data transmission band,corresponding to each one of the plurality of frame offsets, andallocates each frame offset to a plurality of traffic channels so as notto exceed said band management range.
 4. The base station transceiversub-system according to claim 3, wherein said band management range of apredetermined frame offset is determined by a total width where theperiod of said frame offset and the tolerated fluctuation width areadded.
 5. The base station transceiver sub-system according to claim 3,wherein it is checked sequentially whether the remaining datatransmission band in the band management range of each fame offset isgreater than the required band of the traffic channel, and if greater,the frame offset according to said band management range is allocated tosaid traffic channel.
 6. The base station transceiver sub-systemaccording to claim 5, wherein when said frame offset is allocated to thetraffic channel, the remaining data transmission band of the bandmanagement range according to said frame offset is decreased, and theremaining data transmission band of the band management range of anotherframe offset which will be influenced by the allocation of said trafficchannel is decreased.
 7. The base station transceiver sub-systemaccording to claim 5, wherein when a traffic channel is disconnected,the remaining data transmission band of the band management rangeaccording to a frame offset which is allocated to said traffic channelis increased, and the remaining data transmission band of the bandmanagement range of another frame offset which will be influenced bydisconnection of said traffic channel is increased.
 8. A frame offsetallocation method for a base station transceiver sub-system, comprisingan offset allocation block which allocates, to each traffic channel, oneframe offset of N number of frame offsets generated by dividing apredetermined time length T when data is transmitted/received via radioin said predetermined time length frame unit; a radio interface whichtransmits traffic data at a timing according to the frame offsetallocated to said traffic channel when a frame of a predeterminedtraffic channel is transmitted via radio; and a transmission lineinterface block which assembles cells using the traffic data of eachtraffic channel, and transmits/receives the cells to/from the basestation controller via the transmission line at timing according to theframe offset allocated to said traffic channel, wherein said frameoffset allocation method comprises the steps of: tolerating the phasefluctuation of cells on the transmission line for the M frame offsetwidth; and allocating a same frame offset to a plurality of trafficchannels considering the data transmission band determined by saidtolerated phase fluctuation width.
 9. The frame offset allocation methodfor a base station transceiver sub-system according to claim 8, whereinthe band management range according to said tolerated fluctuation widthis set as said data transmission band corresponding to each of saidplurality of frame offsets, and each frame offset is allocated to theplurality of traffic channels so as not to exceed said band managementrange.
 10. The frame offset allocation method for a base stationtransceiver sub-system according to claim 9, wherein it is checkedsequentially whether the remaining data transmission band in the bandmanagement range of each frame offset is greater than the required bandof the traffic channel, and if greater, the frame offset according tosaid band management range is allocated to said traffic channel.
 11. Theframe offset allocation method for a base station transceiver sub-systemaccording to claim 10, wherein when said frame offset is allocated to atraffic channel, the remaining data transmission band of the bandmanagement range according to said frame offset is decreased, and theremaining data transmission enabled band of the band management range ofanother frame offset which will be influenced by the allocation of saidtraffic channel is decreased.
 12. The frame offset allocation method fora base station transceiver sub-system according to claim 10, whereinwhen a traffic channel is disconnected, the remaining data transmissionband of the band management range according to a frame offset which isallocated to said traffic channel is increased, and the remaining datatransmission band of the band management range of another frame offsetwhich will be influenced by the disconnection of said traffic channel isincreased.